Vacuum bagging is a technique used in the manufacturing of structures using composite materials such as carbon fiber reinforced plastics. Major structural components, such as the wing, fuselage, and tail of modern aircraft, such as the Boeing 787 Dreamliner, can be built almost entirely of composite materials. For example, the horizontal stabilizer surfaces of the 787 are built around a composite spar box that is nearly 40 feet long. Typically, a component will include layers of a reinforcing material such as carbon fiber that are laminated together with a liquefied resin that is cured to a solid state to achieve the required structural properties, e.g., strength and hardness, of the component. By providing a vacuum around the component during cure, the vacuum bag can, for example, apply a uniform pressure for holding the lamina together and prevent or remove bubbles in the resin that can weaken the component when finally cured. Vacuum bagging techniques are well developed and include the use of a number of elements, e.g., mold release films, parting layers, bleeder layers, and breathers. Breathers, for example, can be used to distribute and maintain vacuum evenly throughout the bag during the cure process.
The large structures for which vacuum bagging techniques are now used create a new set of challenges for use of the techniques. Complex, co-cure (e.g., in which structural resins and adhesives are cured simultaneously) composite structures often employ highly contoured, heat-seamed vacuum bags, such as for multi-spar box applications and the spar box example given above. To ensure properly manufactured components, proper functioning requires the vacuum bags used in composite fabrication to maintain vacuum throughout handling and cure operations. The bags are typically heat seamed in the longest dimension to allow the operators to place the bags into the final position relative to the component. Due to their dimensions, locating leaks in these bags can be difficult, and most leak detection operations require destructive evaluation (e.g., cutting vacuum ports into the bag) therefore negating the bag's use in the production of composite structures.
Accordingly, there exists a need in the art for methods and systems that allow an operator to identify leaks within a custom vacuum bag without damaging the bag further, allowing the operator to repair the leak or identify the area of the leak for further corrective action.